1. Field of the Invention
The present invention relates to an ejector-type depressurizer for a vapor compression refrigeration system, i.e., an ejector for an ejector cycle.
2. Description of Related Art
As is known in the art, an ejector for an ejector cycle is a kinetic pump which includes a nozzle arrangement and a pressurizer arrangement (see JIS Z8126 Number 2.1.2.3). The nozzle arrangement depressurizes and expands refrigerant to generate high velocity refrigerant flow. In the mixer arrangement, the high velocity refrigerant, which is discharged from the nozzle arrangement, entrains and draws refrigerant from an evaporator, so that the drawn refrigerant (drawn flow) and the discharged refrigerant (drive flow) are mixed, and velocity energy of the discharged refrigerant is converted into pressure energy to increase the pressure of the mixed refrigerant discharged from the mixer arrangement.
That is, in the ejector cycle, expansion energy of the refrigerant is converted into pressure energy to increase the intake pressure of a compressor of the ejector cycle. In this way, the power consumption of the compressor is reduced. However, when the energy conversion efficiency of the ejector, i.e., the ejector efficiency becomes relatively low, the intake pressure of the compressor cannot be sufficiently increased by the ejector, so that the power consumption of the compressor cannot be sufficiently reduced.
At this time, when a flow rate of the refrigerant passing through the refrigerant passage of the pressurizer arrangement is excessively large with respect to the passage cross sectional size (or area) of the refrigerant passage in the pressurizer arrangement, pressure loss induced by friction between the refrigerant and a tube wall of the refrigerant passage is increased, and thus the ejector efficiency is reduced. On the other hand, when the flow rate of the refrigerant in the pressurizer arrangement becomes excessively small with respect to the passage cross sectional size of the refrigerant passage, the entire refrigerant pressure is converted into velocity head (velocity energy), and thus pressure head (pressure energy) becomes small. As a result, the ejector efficiency is reduced.